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Astron. Astrophys. 345, 499-504 (1999)


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A theoretical exploratory investigation on cluster white dwarfs

E. Brocato 1,2, V. Castellani 2,3 and M. Romaniello 4,5

1 Osservatorio Astronomico di Collurania, I-64100 Teramo, Italy
2 Istituto Nazionale di Fisica Nucleare, LNGS, I-67100 L'Aquila, Italy
3 Dipartimento di Fisica dell'Universitá di Pisa, I-56100 Pisa, Italy
4 Scuola Normale Superiore, I-56100 Pisa, Italy
5 Space Telescope Science Institute, Baltimore, MD 21218, USA

Received 7 October 1997 / Accepted 23 November 1998

Abstract

In this paper we present theoretical simulations concerning the luminosity function of cluster WDs, computed under various assumptions about cluster age and IMF. Quantitative evaluations are discussed, showing that the WD cooling sequence can be divided into a portion at large luminosity where the distribution depends on cooling times only, and a narrow interval of luminosities at the bottom of the sequence that gives information about both cluster age and IMF. Detailed theoretical predictions are reported for a range of cluster ages covering the current estimates for the ages of globular and old galactic clusters, discussing theoretical expectations concerning the number ratio of WD to HB stars as a function of both cluster age and IMF. Finally, we discuss old galactic clusters as relevant targets for future observations.

Key words: stars: evolution – stars: luminosity function, mass function – stars: white dwarfs – Galaxy: globular clusters: general – Galaxy: open clusters and associations: general

Send offprint requests to: E. Brocato, Osservatorio Astronomico di Teramo - Collurania Via Maggini, I-64100 Teramo, Italy (brocato@astrte.te.astro.it)

© European Southern Observatory (ESO) 1999

Online publication: April 19, 1999

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